The purpose of this activity is for students to practice adding within 1,000, with an emphasis on adding by place. Throughout the activity, students have opportunities to explain their methods and representations to peers. In the Activity Synthesis, students have opportunities to question and critique the work of their peers as they compare different methods for adding three-digit numbers and different representations that show composing units when adding by place (MP3).

This activity uses MLR8 Discussion Supports. Advances: conversing.

• “How does your representation show that you composed a unit?”
• “What could you add to your representation to help you keep track of any tens or hundreds you compose?”

• Invite 2 or 3 previously identified students to share their representations and how they found the values of the sums.
• “How are these methods the same? How are they different?”

• “How is Noah’s and Kiran’s work the same? How is it different?” (Both show adding by place. Noah used a base-ten diagram and Kiran used equations. They found different values. Noah forgot to add the ten he made from the ones. He had enough tens to make a hundred.)
• “Which student found the correct value for ? How do you know?”
• Invite previously identified students to share.
• Consider asking:
  • “Which step in Kiran’s work did Noah miss?”